The application of a pulling or traction force directed substantially along the longitudinal axis of a human spine is a well known treatment method for providing therapeutic relief to an injured spine. Theoretically, traction provides curative action and relief from pain by stretching the tissue in the spinal column; by "decompressing" the spine to provide additional space between adjacent vertebrae and, consequently, increasing blood flow to the injured spinal vertebrae and tissue; by motion of the spinal vertebrae themselves; or by some combination of the foregoing. Typically, the traction force is applied to a patient who is resting in a supine or prone position on a bed. The traction force is applied by a device that utilizes weights that are suspended vertically from the end of a cord that runs over a pulley having a substantially horizontally disposed rotation axis. The other end of the cord is attached to the patient's body, sometimes to the patient's feet or to a harness surrounding the lower torso. Generally, the prior art traction devices each suffer from having several shortcomings that limit their effectiveness in treating spinal injuries.
First, many of these devices do not take into account the natural curvature of the spinal column, in particular the lumbar segment. The pull of the traction force they provide is directed generally along the axis of the spinal column, which due to this curvature prevents the force from providing the desired separation of the vertebrae.
Second, these devices typically are aimed at providing traction to either the lumbar or cervical regions of the spine, requiring two separate devices being needed to treat these separated spinal regions. Additionally, no known device is able to achieve the application of a traction force in the thoracic area of the spinal column, which lies between the lumbar and cervical areas.
Third, the applied traction force must overcome the frictional force existing between the bed surface and the patient's body. Because the frictional force is usually not accurately known, any accurate assessment of the actual traction force being applied to achieve the desired spinal stretching versus that spent overcoming frictional resistance between patient and bed surface is difficult to make.
Fourth, because of the inability to accurately assess the applied force used for stretching, it is difficult for a physician to know whether the patient is being properly treated. In other words, too little force may be applied to certain patients to achieve any therapeutic benefit and too great a force may be applied to other patients, potentially exacerbating their injuries.
Sixth, in the healing process, the connective tissue surrounding the injured area can bind and constrict. Nerve endings can be impinged upon with resulting pain. Binding and constriction of the connective tissue in one affected area can distort the connective tissue throughout the body. To reduce tissue binding and constriction, the tissue must be permanently plastically deformed. Many, if not all, of the prior art devices operate only in the elastic stress regime of the connective tissue of the spinal column, however. That is, this tissue, e.g., the durameter and the fascia, elastically stretches upon application of the traction force and elastically rebounds upon removal of the traction force. The tissue stretching--and consequent relief for the patient--is therefore of a temporary nature. To produce a permanent stretching and relief, a traction device must therefore safely operate in the tissue's plastic stress regime as well as its elastic.
As is well known, materials, including the connective tissue of the spinal column, exhibit both elastic and plastic qualities depending upon the stress to which they are subjected. On a stress/strain curve the point at which the material begins to exhibit plastic rather than elastic properties is known as the material's yield point. By applying a force to the connective tissue of the spinal column sufficient to stress the tissue past its yield point, a permanent rather than temporary stretching of the tissue may be achieved. Such a yielding of the spinal tissue can only be accomplished in a safe and therapeutic manner if the exact amount of traction force being applied to the spinal column is known with certainty, which is not the case in prior art devices. As noted, if the stress applied to a material is in the elastic region, and thus below the yield point of the material, the material will elastically deform and upon removal of the stress will return to substantially the same configuration and structure as it had prior to the application of the stress. Applying a stress greater than the material's yield point, however, will result in a permanent deformation of the material. Permanent stretching of the connective tissue would ease the compressive pressure felt along the spinal column and will promote healing thereof. Thus, in a treatment where it is desirable to reduce binding and constriction of the connective tissue and to increase the spacing between the individual vertebra, it would be desirable to generate a distraction force to separate the vertebrae and to safely stress the connective tissue of the spine beyond its yield point to achieve a permanent stretching thereof.
Finally, the known traction devices often require considerable bending and movement of the patient's body to get into a proper position for the beginning of therapy. For many patients, any bending can be difficult and painful and is therefore to be avoided during a therapy session if possible.
Some newer traction devices attempt to compensate for such deficiencies just listed. For example U.S. Pat. No. 4,602,619 to Wolf et al. teaches an apparatus and method for applying varying amounts of traction to the spine at an angle to the elongated axis thereof. The apparatus includes a harness placed around and upwardly supporting the patient's pelvic region. A cable is attached at one end to the harness and leads through a pulley attached to an overhead support. The cable may be anchored by means of a cleat attached to the pulley. The overhead support includes a rearwardly and downwardly extending arm connected to an electric screw actuator. In use, the patient pulls on the free end of the cable, thereby raising his pelvic region and substantially simultaneously rotating it. The cable is then anchored and by engaging the actuator, the harness pulley may be moved upwardly and forwardly and then downwardly and rearwardly in alternation to provide a varying amount and direction of force to stretch the spine and to promote healing of damaged spinal areas, particularly in the lumbar area. The patent also makes non-specific claims to being able to treat other portions of the spine with the device.
Thus, a need exists for a traction device that is capable of providing a traction force of known amounts to selected, specific spinal portions. Such a device should be able to carefully and progressively stress the connective tissues of the spinal column into the plastic regime thereof to obtain a permanent stretching of the connective tissue, thereby increasing the space between the individual vertebra.